This invention relates to a fractionation tray for use within a distillation column. It particularly pertains to a novel apparatus and apparatus to minimize the time and cost needed for assembling fractionation trays for use in distillation columns and other related devices in the separation between two or more fluids such as a vapor and a liquid.
Distillation is a method in which a process fluid, typically a vapor and a liquid mixture of two or more substances, is separated into its component fractions of a desired purity, by the application and removal of heat under high pressure or vacuum pressure. Distillation columns are designed to achieve this separation efficiently.
Basic distillation begins from a top portion of a column to a bottom portion of the column. Heavier process liquid flows down the column while lighter process vapor ascends up the column. The main components of distillation columns include a vertical shell, where the separation of the process vapor and liquid substances occurs, and column internals, such as fractionation trays or packings. These column internals increase and enhance the separation between the process vapor and liquid. The internal configurations of the column internals such as tray spacing, column diameter, placement of assemblies to enhance flow increase the efficiency and thereby lead to a lesser requirement of energy.
In a typical distillation column, the fractionation trays are horizontally mounted within the vertical shell. The particular design of the fractionation tray facilitates and enhances the separation between the process vapor and liquid by providing a more intimate contact between the fluids which leads to better separation. Each fractionation tray is comprised of several panels which are typically bolted to each other and subsequently attached by bolting or clamping to a cross-beam support member in the distillation column. The region between each panel and the support member is a xe2x80x9cdead-zonexe2x80x9d where little or no vapor-liquid interaction and separation occurs.
The area of the fractionation tray where the vapor and liquid contact is typically called the active area. The dead-zone regions or area between panels and surrounding the support member is generally subtracted from this area as an inactive area and does not contribute to the separation process. Thus, the combination of the dead-zone regions of all the fractionation trays reduces the efficiency of the column and more trays are required to balance the effect.
Recently, U.S. Pat. No. 5,468,425 to Nutter discloses an apparatus for modifying the dead-zone area of the trays to address the vapor-liquid contact in this area. The substantially large overlapping margin areas between the adjacent panels are provided with substantially geometrically identical apertures between each panel. The large margin areas are required for attaching the adjacent panels together by bolting.
While the addition of apertures in the margin area provides more apertures, the conventional bolts contribute to the same dead-zone problem as in conventional fractionation tray panel designs. Since the overlapping margin areas are significant and run the length of each adjacent panel, the area needed by the bolts to attach each panel together contributes to the dead-zone area. Thus, the benefit of apertures in the margin region are reduced in the capacity and efficiency of the tray and column.
Additionally, the Nutter tray follows conventional tray designs with respect to the installation of such trays by requiring two or more installers. Since each panels is attached to an adjacent panel by a bolt, at least one installer above the tray needs to position and align the bolt hole in one panel with the bolt hole in the second panel. Additionally, an installer must be positioned below the tray to ensure final bolting with either a nut or other locking device. A person skilled in the art will recognize that this conventional installation procedure is a substantial labor cost during the installation of the fractionation tray and contributes to the increased time required for the installation of the distillation column. Thus, there are no labor costs or time savings when required such as during a revamp whereby the entire plant is shut down to accommodate the replacement of the tower internals and any additional non-operational time impacts on the operation of the plant.
Accordingly, there is a need for a fractionation tray which reduces the dead-zone regions between the fractionation tray panels to provide an additional increase in the column capacity and efficiency. The fractionation trays should be easy and simple to construct while retaining enough strength for use in the high pressure vapor and liquid environment. The fractionation tray should also be easy to install to substantially reduce the labor cost and provide time savings during critical installations.
This invention relates to an apparatus for use in the contact between and separation of fluids in a distillation column for mass transfer exchange between two fluids of differing masses. According to the present invention, a fractionation tray surface is provided having first and second interlocking panels and a plurality of valve perforations. The valve perforations allow a lighter fluid such as a vapor flow from below and through the fractionation tray to interact with a heavier fluid such as a liquid flowing above the fractionation tray.
The first interlocking panel has a substantially horizontal flat surface with valve perforations and an alignment area. The alignment area has at least one alignment slot and at least one alignment perforation.
The second interlocking panel is positioned adjacent to the first interlocking panel. The second interlocking panel has at least one alignment tab for insertion into the alignment slot of the first interlocking panel. The alignment tab also contains a valve perforation.
During installation, the alignment tab is inserted into the alignment slot on the first interlocking panel. The valve perforation is aligned with the alignment perforation so that vapor can pass from below and through the fractionation tray to interact with liquid flowing across the surface of the tray.
The fractionation tray and panels are preferably supported by means of an integral truss member positioned at the alignment area. The integral truss member extends down from the alignment area and is designed to minimize interference with the alignment perforation. A flange extends from a foot portion of the integral truss for a stiffening effect to strengthen the truss for support.
In a preferred embodiment, a fractionation valve is inserted into the valve perforation of the alignment tab. The valve may be either a movable or fixed valve. Flooding and weeping are reduced by the use of the valve whereby the vapor ascending from below the fractionation tray is deflecting into a horizontal and lateral flow.
Preferably during installation, no bolts are used to connect the first and second interlocking panels thus minimizing the labor costs during installation. The interlocking panels provide for a quicker installation thereby reducing the time necessary to shut down the plant such as during a revamp operation. Additionally, the lack of bolts allows for a valve perforation to be placed in a traditionally inactive region to reduce the mechanical dead regions of the fractionation tray. This increases the capacity and efficiency of the fractionation tray and distillation column by allowing even greater interaction between the vapor and liquid.
The fractionation tray design of the present invention provides for a quick and easy installation. The alignment system of the panels reduces the cost of the fractionation tray in both labor costs and operating costs by increasing in the capacity and efficiency of the column.